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Biomedical subjects

N Cameron

Publications and source records attributed to N Cameron.

At least 19 recordsLinked to original sources
PubMed2005

Differences in bone size and bone mass between black and white 10-year-old South African children.

INTRODUCTION: Black and white South Africans hail from vastly disparate cultural and socio-economic backgrounds the result of which exposes black children to numerous factors known to impact negatively on bone mass. Thus, we studied ethnic differences in bone size and bone mass between 476 10-year-old black and white South African girls and boys (black boys n=182, white boys n=72, black girls n=158, white girls n=64) who formed part of a longitudinal cohort of children born in Johannesburg, South Africa, during 1990. METHODS: Bone area (BA) and bone mineral content (BMC) were measured at the whole body, total hip, femoral neck, lumbar spine (L1-L4) and mid- and distal radii by dual energy X-ray absorptiometry (DXA). Vertebral heights and metacarpal indices were measured. Anthropometry, skeletal maturity and pubertal development were also assessed. RESULTS: After correction for height, weight, gender and puberty, black children had greater BMC at the femoral neck (P<0.0001), total hip (P<0.05) and mid-radius (P<0.001) than white children.. At the whole body, lumbar spine, and distal one-third of the radius, there were no differences in BMC between black and white children after correction for differences in body size. After correction for height and puberty, vertebral heights were less in black children than white children, and cortical areas at the second metacarpal were greater in black children. CONCLUSION: These findings suggest that, at the femoral neck, total hip and mid-radius, these differences are not a result of differences in anthropometry, bone age or pubertal stage, or environmental factors but are most likely to result from genetic differences.

Absorptiometry, Photon↗
PubMed2004

Associations between physical activity and bone mass in black and white South African children at age 9 yr.

We investigated differences in physical activity (PA) levels between black and white South African 9-yr-old children and their association with bone mineral content (BMC) and density (BMD) by using dual-energy X-ray absorptiometry. PA was analyzed in terms of a metabolic (METPA; weighted metabolic score of intensity, frequency, and duration) and a mechanical (MECHPA; sum of all ground reaction forces multiplied by duration) component. There were significant ethnic differences in patterns of activity. White children expended a significantly greater energy score (METPA of 21.7 +/- 2.9) than black children (METPA of 9.5 +/- 0.5) (P < 0.001). When children were divided into quartiles according to the amount and intensity of sport played, the most active white children (using METPA scores) had significantly higher whole body BMD and higher hip and spine BMC and BMD than less active children. White children in the highest MECHPA quartile also showed significantly higher whole body, hip, and spine BMC and BMD than those children in the lowest quartile. No association between exercise and bone mass of black children was found. In this population, PA has an osteogenic association with white children, but not black children, which may be explained by the lower levels of PA in the black children. Despite this, black children had significantly greater bone mass at the hip and spine (girls only) (P < 0.001) even after adjustment for body size. The role of exercise in increasing bone mass may become increasingly critical as a protective mechanism against osteoporosis in both ethnic groups, especially because the genetic benefit exhibited by black children to higher bone mass may be weakened with time, as environmental influences become stronger.

Activities of Daily Living↗
PubMed2004

Relationships between media use, body fatness and physical activity in children and youth: a meta-analysis.

OBJECTIVE: To review the empirical evidence of associations between television (TV) viewing, video/computer game use and (a) body fatness, and (b) physical activity. DESIGN: Meta-analysis. METHOD: Published English-language studies were located from computerized literature searches, bibliographies of primary studies and narrative reviews, and manual searches of personal archives. Included studies presented at least one empirical association between TV viewing, video/computer game use and body fatness or physical activity among samples of children and youth aged 3-18 y. MAIN OUTCOME MEASURE: The mean sample-weighted corrected effect size (Pearson r). RESULTS: Based on data from 52 independent samples, the mean sample-weighted effect size between TV viewing and body fatness was 0.066 (95% CI=0.056-0.078; total N=44,707). The sample-weighted fully corrected effect size was 0.084. Based on data from six independent samples, the mean sample-weighted effect size between video/computer game use and body fatness was 0.070 (95% CI=-0.048 to 0.188; total N=1,722). The sample-weighted fully corrected effect size was 0.128. Based on data from 39 independent samples, the mean sample-weighted effect size between TV viewing and physical activity was -0.096 (95% CI=-0.080 to -0.112; total N=141,505). The sample-weighted fully corrected effect size was -0.129. Based on data from 10 independent samples, the mean sample-weighted effect size between video/computer game use and physical activity was -0.104 (95% CI=-0.080 to -0.128; total N=119,942). The sample-weighted fully corrected effect size was -0.141. CONCLUSION: A statistically significant relationship exists between TV viewing and body fatness among children and youth although it is likely to be too small to be of substantial clinical relevance. The relationship between TV viewing and physical activity is small but negative. The strength of these relationships remains virtually unchanged even after correcting for common sources of bias known to impact study outcomes. While the total amount of time per day engaged in sedentary behavior is inevitably prohibitive of physical activity, media-based inactivity may be unfairly implicated in recent epidemiologic trends of overweight and obesity among children and youth. Relationships between sedentary behavior and health are unlikely to be explained using single markers of inactivity, such as TV viewing or video/computer game use.

Adolescent↗
PubMed2004

Unexplained HIV-1 infection in children--documenting cases and assessing for possible risk factors.

BACKGROUND: In the year 2000 we reported possible horizontal transmission of HIV-1 infection between two siblings. An investigation of three families, each with an HIV-infected child but seronegative parents, permitted this finding. Sexual abuse and surrogate breast-feeding were thought unlikely. The children had overlapping hospitalisation in a regional hospital. Since then several cases of unexplained HIV infection in children have been reported. A registry was established at Tygerberg Children's Hospital for collection of data on the extent of horizontal or unexplained transmission of HIV in children. STUDY DESIGN: Retrospective chart review. RESULTS: Fourteen children were identified, 12 from the Western Cape and 1 each from the Eastern Cape and KwaZulu-Natal. Thirteen (92%) had been hospitalised previously. In the Western Cape, children had been hospitalised in 8 hospitals. Ten of 13 (77%) were admitted as neonates and 9 of 13 (69%) had 2 or more admissions. Intravascular cannulation and intravenous drug administration occurred in all but 2 children before HIV diagnosis. CONCLUSION: We have confirmed HIV infection in a number of cases where the source of infection has been inadequately explained. Circumstantial evidence supports but does not prove nosocomial transmission. Further studies and identification of medical procedures conducive to the spread of HIV are urgently needed.

Age Distribution↗
PubMed2002

Growth reference charts for use in the United Kingdom.

Since the introduction of new growth charts in the mid 1990s, there has been confusion about which charts should be used, with many districts using more than one version. Because of this uncertainty, an expert working party, the Growth Reference Review Group, was convened by the Royal College of Paediatrics and Child Health to provide guidance on the validity and comparability of the different charts currently in use. This paper describes the technical background to the construction and evaluation of growth charts and outlines the group's findings on the validity of each growth reference in relation to contemporary British children. The group concluded that for most clinical purposes the UK90 reference is superior and for many measures is the only usable reference that can be recommended, while the original Tanner-Whitehouse and the Gairdner-Pearson charts are no longer reliable for use at any age. After the age of 2 the revised Buckler-Tanner references are still suitable for assessing height. There are presently no reliable head circumference reference charts for use beyond infancy. The group propose that apart from refinements of chart design and layout, the new UK90 reference should now be "frozen", with any future revisions only undertaken after careful planning and widespread consultation.

Adolescent↗
PubMed2000

Relation between weight gain and beta-cell secretory activity and non-esterified fatty acid production in 7-year-old African children: results from the Birth to Ten study.

AIMS/HYPOTHESIS: This study aimed to assess the effects of fetal and childhood growth on beta-cell activity and insulin sensitivity in 7-year-old children. METHODS: Insulin, des-31,32 proinsulin, proinsulin, non-esterified fatty acids and glucose concentrations were measured in oral glucose tolerance tests in 152 South African children for whom longitudinal weight data was available. RESULTS: Children with low weights at birth and 7 years (low-low) had relatively low beta-cell activity whereas children with low birth weight and high weight at 7 years (low-high) had relatively high beta-cell activity. The low-low group had higher 30-min glucose concentrations than children with high birth weights. When each insulin-related peptide was expressed as a percentage of all these peptides the low-low children had the highest percentage of insulin but the lowest of the prohormones. The low-high children had the lowest percentage of insulin but the highest of the prohormones. Non-esterified fatty acid concentrations were lowest and their suppression post-glucose load highest in the low-high group. CONCLUSION/INTERPRETATION: Poor fetal and neonatal growth give rise to low beta-cell numbers compensated for by increased efficiency of proinsulin processing to insulin. Poor fetal followed by higher postnatal growth results in low beta-cell numbers and reduced whole-body glucose uptake which leads to reduced efficiency in the processing of proinsulin. Growth in utero and postnatally therefore have profound effects on beta-cell activity and insulin sensitivity with poor fetal coupled with high postnatal growth being detrimental to these processes but not detrimental to the suppression of lipolysis.

Analysis of Variance↗
PubMed2000

The accuracy of body weight and height recall in middle-aged men.

OBJECTIVE: To determine the accuracy of recalled height and weight, and calculated body mass index (BMI), over a 27-37 y period. DESIGN: Comparison of measured height and weight with recalled height and weight 27-37 y later. PARTICIPANTS: Two hundred and twenty-five men measured aged 18-24 y as physical education students at Loughborough Training College, UK, between 1958 and 1967. RESULTS: Initial body weights were over-estimated by 3.1 +/- 4.5 kg and heights by 1.1 +/- 1.8 cm, on average. Some 42% (95) of recalls were within 2.5 kg and 79% (178) within 2.5 cm, resulting in 58% (130) of the differences in BMI calculated from recalled and actual heights and weights to be within 1 kg/m2. However, 29% (66) of recalls were more than 5 kg and 8% (19) more than 10 kg from the measured values. Weight errors (actual-recalled) were negatively related (r = -0.43, P < 0.001) to weight gain over the 27-37 y interval. CONCLUSIONS: Middle-aged men who were formerly physical education students recalled their previous height and weight well, in most cases, 27-37 y later. The bias from recalled data would be to underestimate weight gain by 3 kg and BMI by 1 kg/m2, on average. Errors of more than 5 kg in 29% of participants and of more than 10 kg in 8% would be expected to interfere seriously with attempts to show epidemiological relations between early weight based on recall and subsequent outcomes.

Bias↗
PubMed2000

Cardiovascular disease risk factors in 5-year-old urban South African children--the Birth to Ten Study.

BACKGROUND: A birth cohort study, the Birth to Ten (BTT) study, commenced in the greater Johannesburg/Soweto metropole in South Africa in 1990. The overall BTT project collected antenatal, birth and early development information on these children as well as information that could help identify factors related to the emergence of risk of cardiovascular diseases (CVDs) in children. OBJECTIVE: To determine CVD risk profiles and their determinants in 5-year-old children living in an urban environment in South Africa. METHODS: Demographic and birth characteristics were collected on a sample of 964 5-year-olds whose parents agreed for blood samples to be taken from their children. The children's height and weight were measured using standardised procedures; blood pressure (BP) was measured with a Dinamap Vital Signs Monitor, and a non-fasting blood sample was drawn for lipid determinations. Information on exposure to tobacco smoke and additional health-related data were obtained by interview. RESULTS: No differences were found between the birth weight and gestational age of the 5-year-old CVD participants and the remainder of the children studied at birth. The systolic BP was significantly different between ethnic groups, with the BP of the black children significantly higher than that of the Indian and white children, while the diastolic BP of black children was also the highest. White children had the highest mean total cholesterol (TC) and low-density lipoprotein cholesterol (LDLC) levels, significantly higher than those in the black community. The coloured children's TC level was also significantly lower than that of the whites, while the LDLC level of the Indian children was significantly higher than that of the blacks. Overall, 64% of the children were exposed to environmental tobacco smoke (ETS), with the white group having the lowest rate (45% exposed to ETS). The coloured children were most frequently exposed to ETS, with 40.6% having primary caregivers who smoked; of these children 42% lived in homes with two or more smokers. CONCLUSIONS: Tobacco control legislation will protect South Africans against tobacco sales promotions. This will be the first step towards increasing the priority of chronic disease prevention, health promotion and appropriate care for chronic diseases and their risk factors on the South African health policy agenda. The groups of children that were studied carried differing but significant levels of CVD risk. This suggests that the promotion of a healthy lifestyle should start in childhood, and should target the risk factors found in each group.

Analysis of Variance↗
PubMed1999

An inverse relation between blood pressure and birth weight among 5 year old children from Soweto, South Africa.

STUDY OBJECTIVE: To examine the relation between birth weight and blood pressure at 5 years in a cohort of South African children. DESIGN: Prospective cohort study. PARTICIPANTS: 849 five year old children. SETTING: Soweto, a sprawling urban area close to Johannesburg, South Africa, which was a designated residential area for people classified as "black" under apartheid legislation. MAIN RESULTS: Systolic blood pressure at 5 years was inversely related to birthweight (r = -0.05, p = 0.0007), independent of current weight, height, gestational age, maternal age or socioeconomic status at 5 years. There was no relation between birth weight and diastolic blood pressure. After adjusting for current weight and height, there was a mean decline in systolic blood pressure of 3.4 mm Hg (95% confidence intervals 1.4, 5.3 mm Hg) for every 1000 g increase in birth weight. CONCLUSIONS: These data from a disadvantaged urbanised community in Southern Africa extend the reported observations of an inverse relation between birth weight and systolic blood pressure. The study adds to the evidence that influences in fetal life and early childhood influence systolic blood pressure. Further research is required to assess whether efforts to reduce the incidence of low birthweight babies will attenuate the prevalence of hypertension in future generations.

Birth Weight↗
PubMed1998

Association between poor glucose tolerance and rapid post natal weight gain in seven-year-old children.

A number of studies have shown that glucose tolerance falls with decreasing birth weight and that people with low birth weight and high body mass index (BMI) as adults are those at greatest risk of developing Type II (non-insulin-dependent) diabetes mellitus. No such studies have been carried out in African populations. Therefore we investigated the relation between glucose tolerance and birth weight in a group of 7-year-old black South Africans for whom longitudinal anthropometric data were available. Oral glucose tolerance tests (OGTTs) were carried out on 152 subjects and inverse correlations were found between birth weight and the total amount of insulin secreted during the first 30 min (r = -0.19, p = 0.04) and last 90 min (r = -0.19, p = 0.04) of the oral glucose tolerance test and also between birth weight and the 30 min glucose concentrations (r = -0.20, p = 0.02). Children born with low birth weights but who had high weights at 7 years had higher insulin concentrations and indices of obesity compared with those with low birth weights and low weights at 7 years. There were also positive correlations between weight velocity and BMI (r = 0.24, p = 0.02) and weight velocity and insulin resistance (r = 0.18, p = 0.04) as measured using homeostasis model assessment (HOMA). Thus, low birth weight in conjunction with rapid childhood gains in weight especially as subcutaneous fat, produces poor glucose tolerance in 7-year-old children and can make them susceptible to the development of Type II diabetes later in life.

Birth Weight↗
PubMed1997

Sex differences in the prevalence of obesity in rural African adolescents.

OBJECTIVE: To investigate the prevalence and gender differences in obesity in rural African adolescents. DESIGN: Cross-sectional analysis of a mixed-longitudinal study. SUBJECTS: Four hundred and forty-seven rural African adolescents (190 females; 257 males) aged 7.0-18.9 y. MEASUREMENTS: Anthropometric measurements of height, weight, and skinfolds at the bicep (BCP), tricep (TRCP), subscapular (SSCP) and suprailiac (SPIL) sites and derived ratios of fat distribution including trunk:limb ratios (SSTB = (SSCP + SPIL)/(TRCP + BCP) and ST = SSCP/TRCP), and the upper:lower truncal ratio (TRUNK = SSCP/SPIL). Obesity was defined as (1) a BMI greater than the NHANES III 85% centile or (2) the sum of TRCP and SSCP skinfolds greater than the NHANES III 85% centile. RESULTS: Skinfold measures were significantly greater in females throughout the age range but remarkably greater divergence was apparent after mean menarcheal age of 14.03 y (s.d. = 1.25). Centralization of body fat was consistently greater in males but only significantly so after 14 y of age for the ST ratio. Obesity, defined by BMI or sum of skinfolds, was greatest in females following menarche reaching a maximum of 16.7% by BMI and 11.1% by sum of skinfolds, and almost non-existent in males. CONCLUSIONS: Increased prevalence of obesity in African females did not occur throughout adolescence but was linked to the timing of menarche. Increased fatness and obesity appears to be a post-menarcheal phenomenon probably caused by the hormonal changes leading to and following first menstruation.

Adolescent↗
PubMed1997

The organisation of a national survey for evaluating child psychomotor development in Argentina.

A total of 211 selected paediatricians were invited to participate in a national survey designed to evaluate the age of attainment of developmental milestones in children aged 0-5 years. Following a pilot study and a cascade training design, 61.1% of the paediatricians successfully completed the data collection on 139 developmental items. In the pilot study, there were more missing (not performed) items in children over one year of age, thus confirming the impression that paediatricians are more familiar with evaluating development in infants. However, in the age range 1-5 years, there were significantly fewer missing items in the gross motor area than in the other areas. Following a training programme and data editing and cleaning, a final sample of 3573 healthy, normal children was obtained. The impact of the training process was significant, in the sense that 3.5% of the items in children older than one year were not performed by the paediatricians before training, but this percentage was reduced to 1.9% after training (P < 0.01). The sample formed 0.11% of the national population less than 6 years of age and included a sex ratio of 1.01 compared with a national ratio of 1.02. There were no significant differences in the geographical distribution of the sample in comparison with that of the national population. The social composition, assessed by maternal education level, was biased towards a better education level than the national population. Mean Z-scores for height and weight were not significantly different from zero, when calculated on the basis of the national growth standards. In addition to successfully obtaining a representative sample for the analysis of the age of attainment of developmental milestones in Argentinian children, the survey also accomplished an educational objective in the training of paediatricians in developmental paediatrics.

Argentina↗